package com.wdc.simple.day01;

import java.util.ArrayList;
import java.util.Scanner;

public class Main01 {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        ArrayList<Object> list = new ArrayList<>();
        String line = scan.nextLine();
        for (int i = 0; i < line.length(); i++) {
            char c = line.charAt(i);
            if (list.contains(c)){
                System.out.println("NO");
                return;
            }
            if (ignore(c)){
                char lowerCase = Character.toLowerCase(c);
                if (!(list.contains(lowerCase))){
                    list.add(lowerCase);
                }else {
                    System.out.println("NO");
                    return;
                }
            }else {
                list.add(c);
            }


        }
        if (list.size() == line.length()){
            System.out.println("YES");
        }
        scan.close();
    }

    //判断是否是字母 如果是字母则返回true
    public static boolean ignore(char ch){
        if (ch >= 'a' && ch <='z' || ch >= 'A' && ch <='Z'){
            return  true;
        }else {
            return false;
        }

    }
}
